On March 30 of this cool spring, the year-old test planting was showing no sign of breaking dormancy.

On March 30 of this cool spring, the year-old test planting was showing no sign of breaking dormancy.

Sweet cherry growers are in transition from orchard systems they know—and don’t like much—to new systems they don’t know, but hope they’ll like better.

Some things they do know. Trees will be smaller, probably on a Gisela rootstock but possibly others. Pruning will be different. Trees might be freestanding, or they might be on a trellis. They might look very much like the new apple orchard systems—or they might look very different, as with the Upright Fruiting Offshoot concept.

As growers ponder and try to make good decisions, researchers across North America are collaborating, seeing what works best in their regions and making adjustments as they go. “We’re not just studying training systems, we’re developing them on the go,” says Dr. Greg Lang at Michigan State University.

As part of an NC-140 project evaluating rootstocks for new orchard systems, Lang and researchers at ten other sites across North America have planted coordinated sweet cherry trials.  At three sites—MSU at Clarksville and Cornell University’s plots at Geneva and Hudson Valley—four training systems are being studied and adapted: TSA—the acronym for tall spindle axe; SSA, short for slender spindle axe; KGB, for Kym Green bush (a modification of the Spanish bush); and UFO, the initials for Upright Fruiting Offshoots, developed by Dr. Matt Whiting, horticulturist with Washington State University (see “Cherry systems explained”).  The other eight NC-140 sites, which extend from Mexico to Canada, only have the TSA, KGB, and UFO systems under study.

Michigan State University is evaluating the four systems with the variety Benton; ­Cornell University’s Dr. ­Terence Robinson and Dr. Steve Hoying are conducting their evaluations with Regina. New York and Michigan growers share a similar Great Lakes-moderated, humid climate—and they see new regional market opportunities, with the growing “local foods” movement, to supplement the fresh market sweet cherry industry now dominated by California and the Pacific Northwest.

High-density tour

Lang spoke to about 70 Michigan sweet cherry growers March 30 on what was called “the high density cherry tour” that took them to the Clarksville Horticultural Experiment Station and to orchards of growers trying new concepts.

Lang’s Clarksville planting was established with sleeping eye trees in 2009 and completed with nursery trees in 2010. Trees were planted in groups of four (or eight for SSA) along trellises of high-tensile nylon “wires,” with each system replicated six times. Each system was duplicated with trees on Gisela 3, 5, or 6 rootstock, and planted about five feet apart, except the SSA, which was planted at 2.5 feet. Some things need to be studied under humid Great Lakes region conditions, such as, how much ­pruning growers can do.

“Pruning and sharp angles have never been recipes for success in our region,” Lang said. Bacterial canker is a problem, and so far, Lang is controlling it by dormant pruning in dry conditions and following each with a fixed copper spray application. Still, he is concerned that the KGB system might be canker-prone in the Great Lakes ­climate, and also may not let enough light penetrate into the dense canopy.

Will growers need trellis and wires? Three of the systems are freestanding, but the UFO needs trellis—and trellis wire rubs lead to more bacterial canker, growers believe. Lang is testing that, and also using plastic wires to see whether that makes a difference.

Trees are being grown over a fabric weed barrier between double irrigation lines, and fertilization is done through the irrigation water. Fertilizer is applied with every application of water from April through mid-July (bloom to postharvest). In September, two foliar applications of urea (3 percent solution) are made to boost the trees’ nitrogen reserves for the next season—without encouraging late-season growth that would be susceptible to winter injury.  This late-summer foliar application also improved fall cold acclimation, according to research by Lang’s recent graduate student Theoharis Ouzounis.

No matter which system performs best, growers will share in a learning experience. The new systems all require that growers know more about plant physiology—about how cherries grow and fruit, and what effect their orchard practices, especially pruning, have on the yield, size, and sweetness of their fruit.

With three of the systems, trees have a fruiting wall architecture, and Lang thinks these will be best suited to mechanization. Machines like platforms or string thinners work best with the fruiting wall concept. All four systems will be labor-friendly—no ladders needed taller than one- or two-step size.